Seagull Survey (Part IV)

The May Day weekend was a busy one at Isla Perdiguera, with hordes of yotties turning up to enjoy a barbecue on the beach or a rather chilly dip in the sea. Unfortunately, quite a few also took a ramble around the island, so that the yellow-legged gulls raising their young on the hillsides had rather a stressful time. The Ship’s Naturalist was there, keeping an eye on her friends and proteges.

On May the 2nd we were walking round the island, visiting the usual yellow legged gull nests but in the opposite order from usual. We were just coming out of the thorn bushes in the valley and still about 100 yards from the beach when Mummy started to shout.

“Roxanne! Get that chick!” she was yelling.

I looked round and there was a chick, quite a big one, running into the sea! The sea on this side of the island was quite rough, so that he could not possibly survive. I got quite wet rescuing him, and he sicked up his lunch, which is quite usual for a chick which is in a panic. (It happened to be the guts of something, a young rabbit probably, or a rat. I think that gulls eat rabbits quite often.)

We continued with our inspection and when we got back round to the other side of the island Mummy went for a walk along the beach. Suddenly she was calling me again.

“Roxanne, there’s another chick in the sea!”

This time she had seen the chick go into the sea when he was a very long way away. He was already a long way out. I rushed to get the dinghy – but I never found him. At the time we thought that he had sunk.

Since then we have seen many chicks swimming. I suppose it is not so surprising really. After all, ducklings can swim while they are still small and fluffy. Often a family of two or three seagull chicks goes into the water together, and sometimes two families go together. Several times we have seen the mother and father fly out and land beside her brood. Once three little chicks ran into the sea and swam, and their mother flew out and herded them together and led them back to the shore!

The chicks that we have seen swimming are never the very tiny ones. They seem to start at about two weeks old. At first the sea is a place to run and hide when danger is approaching. Once they are a month old then the chicks who live by the shore go swimming often for the fun of it, and the bigger ones go a very long way out.

Mummy spends her whole time puzzling over the gulls.

“Why are some of the nests out in the open, with no shelter? Why do some of the chicks run, instead of hiding?”

The question we ask ourselves most is “Why do the gulls dive bomb us?”

Obviously they are trying to drive us away from their nests.

“But it doesn’t work. It has the opposite effect.” says Mummy. “You’re walking along, not aware of any nest being nearby, and then you suddenly started getting scolded. That’s the first clue. Then when you’re really near the nest they start to dive bomb you. It’s a bit like a that game where you have to keep asking, “Am I getting warmer?” The nearer we get to the chicks, the more the parents dive bomb us. They actually show us where their chicks are hiding!”

It’s true. Almost half of my 107 nests have been pointed out to me by the gulls. They give you all the information. They show you where the nest is, whether there are chicks, and how old they are, from the amount of bombing. But birds are not especially evolved to cope with humans. They are evolved to deal with other animals – such as foxes. By the time a fox has come near enough to be bombed it has quite likely smelled the chicks anyway. The sooner it is discouraged, the better. I have been hit quite hard by gulls and it hurts. I don’t think a fox would like it! (They also drop their nasty white bombs – but perhaps a fox would mind that less than we do. JDS)

Another interesting thing is the way the parents behave differently. The mother of the chicks in N9 (Remus’ mother) was so upset when I picked up one of Remus’ brothers that she sicked up a great gob of food. The parents of the chicks in N65 have hit me on the head three times while they dive-bomb. The parents of the chicks in the beach nest (N99) do very feeble dive bombing, swoopng far above my head. And the parents of N11 have never even been seen. For a long time I thought this nest was abandoned. It was almost as old as N9 and N7 (the nests from which Romulus and Remus came) but it only had two eggs. I thought that the mother had laid two eggs, and died before laying the third. Then, on May the 2nd, we found that the eggs had hatched. But the parents still didn’t bomb us or scold us or pay us any attention at all. Perhaps this was because the mother had died and the father was managing to look after the chicks alone. Perhaps usually the mother bombs the most. (I think this is most unlikely – I very much doubt whether one parent could hatch and raise the chicks alone. JDS)

Some people think that gulls are aggressive, but we have watched and we think that perhaps gulls are all different characters, like people. A few gulls seem to have an instinct to attack other weaker gulls. We have seen sick birds and chicks which were swimming getting dive-bombed by other birds. Sometimes we see a chick on the island getting attacked by an adult, and often an actual fight follows, with two or three adults pulling at each other’s tails, and often one bird holding another by the beak. I suspect this happens when a chick leaves its own territory and goes too close to another bird’s nest. The gulls always drive off other gulls which come onto their territory.

We used to think that the birds dive-bombing the chicks on the water were bullies. It’s never all of the birds that do it. Usually it is just one or two. But Mummy thinks it might be that they are not bullying at all. She thinks they might be trying to encourage the juvenile or the sick bird to fly. I don’t agree, but it’s true that the birds never actually get hit. And sick birds sitting on the land never get mobbed at all.

Always when you walk around Isla Perdiguera you find dead seagulls. At first I thought this was perfectly natural. There is such a huge population of gulls and the old ones have to die sometime. But it is now clear that something is killing the gulls. There is some kind of illness which makes the birds weaker and weaker until they can’t fly, and then they die of hunger and thirst. Their eyes become half closed and they are unable to open them properly. This could just be dehydration, or it could be part of the illness.

Six times I’ve found a dying bird. The first time we took it back to the boat and fed it with a syringe, but after four days it died. The second time we left it be, and after three days it died. The most recent time we took the sick bird and hid it safely under a bush, and we gave it water wih a syringe. The next day it was gone, so I suppose I must have flown away.

I think that this is the best thing to do with an ill animal. If you take it away it is sad and scared, because it has left its natural surroundings.

(The photo shows a two year old bird which was smitten with the mystery illness.

Like herring gulls, yellow-legs go through four identifiable phases after fledging. The one year olds are speckled brown all over, and the three year olds still have a little bit of brown on the leading edge of their wings. This is not because they still have some of their very first feathers left. Indeed, seagulls moult twice a year – although they only change their wing feathers once a year, at the autumn moult.

We don’t see any one year olds at Perdiguera. We see quite a few two and three year olds, but it seems that only the fully paid up adults, of four years plus, are capable of breeding. None of the sub-adults lives up to the family name. They all have pink legs. JDS)

One of the nature wardens from Isla Grosa (the nearby Audoin’s seagull colony) told us that the illness which kills the gulls is botulism! Mind you, he has told us many things before which turned out to be wrong… Whatever it is, the biologistas (government paid naturalists, or ecologists) have a much nastier method of getting rid of the gulls – several methods in fact. They do not want the yellow-legged gulls to nest on Isla Grosa, because they are afraid that they will attack the Audoin’s, so at the egg laying time they go around punching holes in the eggs, so that the unborn chick dies. This year that still left a lot of gulls sitting around on the island, and so a few weeks a go they put little bits of poisoned bread beside the nests. Apparently the parents eat the bread and then, within five minutes they fall out of the sky, dead! I suppose the chicks starve. It seems rather cruel to do it at this time of year, when the chicks are around. Why couldn’t they have done it earlier, when there were no chicks, instead of making them suffer?

(We have not found very many addled eggs on Perdiguera, so we don’t think that the “biologistas” spiked any here. On the other hand, we have recently seen quite a number of dead gulls, lying spread-eagled on the ground, and a few weeks ago the professionals certainly did pay a visit to collect some seagull chicks. These were bound for a new, Terra-Mitica-style theme park in Murcia. According to their boatman, they took 20 chicks and 10 eggs. This undoubtedly explains why some of “our” nests are one chick short. It is rather a nuisance since one of the purposes of Roxanne’s study was to see whether it is really true that the parents are only able to feed one, or at best two chicks, and that the surplus starves. JDS)

It is getting harder to find the chicks nowadays when we go ashore. That is because most of them have hatched some time ago and they are big enough to run and hide. Big chicks can run as fast as we can, and they can scuttle under bushes. We must pass many by without seeing them. Their parents tell us that they are there, and we search, but still we often can’t see them. The big ones are in the bushes, but the little grey fluffy chicks can look just like another stone on the hillside. Twice Mummy has very nearly trod on one!

Usually we only see the chicks which run, but sometimes we catch glimpses of chicks which are as big as our two – big chicks with feathers all over them. We usually only see these big juveniles while we are watching from the boat, with binoculars. Then you can usually work out who you are seeing, and which nest they come from, because the chicks stay on their territory.

The territory around each nest seems to be about fifty or a hundred feet wide. One parent is always on guard, in the middle of the territory, ready to drive off other gulls. We have notice that it seems to be always the same parent, and we think it is probably the mother. The other bird goes away to get food, and he is usually away for hours. When he comes back the gulls both stretch out their necks and greet each other, “ka ka ka ka ka kaa kaaa.” This noise is going on all the time on the island, because there are always birds returning to the nest with food, so it is a very noisy place. The parent seems to spit the food onto the ground, but it’s hard to see because it always seems to happen behind a bush! When the chick meets the parent it bobs up and down and cheeps loudly. Remus does this all the time whenever he sees me, but Romulus doesn’t do it very often. Sometimes both gulls are standing there together, especially if the eggs are still being incubated. One bird sits on the nest, and the other one stands beside it and keeps watch very carefully. When we walk past the nests there are usually two birds bombing us, so it could be that the one who is supposed to be off getting food is actually quite nearby, with his mates. (Typical male behaviour…JDS)

I have come to the conclusion that Remus is not so very odd, after all, in swallowing a pencil. We thought that he did it because he had been brought up by humans instead of by birds, but it seems that it may be quite usual for a bird to eat whatever it finds. I have some pellets which I found beside seagull nests and which I am almost certain come from seagulls. Some contain fairly sensible things like rabbit bones, fish bones and seeds, but one has plastic in it and another even has pieces of glass! I also found a pink felt pen which looked as if it had been chewed and swallowed, and once when I picked up a fairly small chick it sicked up quite a big feather.

Romulus and Remus are now great big birds with big, long wings. And to think that six weeks ago they were just tiny fluffy things! They have no fluff left on them anymore. On the 12th of May we ringed them – not with metal rings, as we don’t have any yet, but with coloured cable ties. Now we have Remus-the-red and Romulus-the-green. In a few days they will be flying, and we want to be sure that we can always recognise them. We don’t know how far they will fly, but we have heard of six month old yellow-legged gulls travelling all the way across Spain from Murcia to Galicia. So if you happen to see a very friendly yellow-legged gull with a red or green band on its leg, please be nice to it – and let us know!

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Roxanne is the only one of our ship’s company who can claim that she was actually born aboard a yacht. She can also claim to be the youngest sailor amongst us, having made her first channel crossing (from England to France) at two weeks of age. Her first birthday was spent a few days out from Cape Town, and her fifth one day out from the South Atlantic island of St Helena.

Two of Roxanne’s first three years were spent living on a farm and her early interest in everything from earwigs to ostriches formed the foundation of her passion for wildlife. At the age of eight Roxanne won first prize in the RSPB’s Nature Diary competition in the 8 – 12 year olds category, and a couple of years afterwards she was asked to write an article for their junior magazine.

Excellent field report and observations Roxanne… I am looking forward to the next instalment…

I would be interested in the name of the chemical used in the poison bread that you have mentioned. Placing any kind of poison bait down in any environment also has an effect on other wildllife. (Normally negative)… I would also like to know if the yellow leg is totally responsible for the decline of the audoin… If it isn’t what is?

Sorry Clive, I’ve just received a text saying our friend doesn’t know what the poison is… 🙁
I don’t know whether the yellow-legs are entirely responsible for the decline of the Audoin either. I think Rox thinks they aren’t responsible at all – but the biologistas certainly seem to think they are.

Great work Roxanne…do you think that the dive bombing nest defence tactics may depend on the age and experiences of an adult bird? Maybe those that do not bother to attack or just make a feeble attempt are older birds and the fierce ones are first timers…or even vice versa!

I’m sorry for the long delay in replying to your comments. There’s no internet connection at Isla Perdiguera! 🙂 This is also my excuse for having been so long in getting round to posting the next part of Roxanne’s article.

Clive, I have spoken to our friend. He does not know the name of the poison which is doled out to the gulls but he said that it is used selectively and in a very controlled manner, the aim being to ensure that it cannot enter the food chain. The poison is deposited adjacent to the nests of the intended victims, the birds return and eat the bait… and half an hour later the “biologistas” round up the corpses.

As Roxanne says, it seems particularly unfair that they should choose to cull the birds during nesting time – although it is possible that they only do it to birds with unhatched eggs. Indeed, one likes to think that this must surely be the case…

It isn’t nice, but then killing and culling never is, and so far as these people are concerned they are doing it in the interests of preserving an endangered species – the Audouin’s. Having now watched the yellow-legs in action at their nesting site I have to say that any other species sharing the same rock would certainly be in mortal danger. Adult Audouin’s are perfectly capable of holding their own against the yellow-legs, but a chick would be regarded as fair game / dinner. The yellow-legs even attack the young of their own kind, although so far as we have been able to tell they aren’t actually cannibalistic.

There are a lot of dead gulls on Perdiguera, and every week or two we find a new cadaver. Based on what we have now been told it seems clear that these are not the work of the Naturalists. Our friend reckoned that one death per fortnight was about par for the course with a colony of this size. He said that the birds die through having eaten the wrong sort of things at the dump.

As we have seen, gulls certainly do eat some stupid things… but the sick gulls that we encounter appear to be dying of an illness rather than through bowel obstruction. (Mind you, having said that, I don’t know what the symptoms of ingesting a plastic bag might be.) I guess that the dump is full of all sorts of unsuitable things, and all sorts of rotten things too. Gulls are probably almost as susceptible as we to salmonella – and to botulism.

As for the Audouins – no, I don’t see that the yellow-legged gulls could be responsible for the decline in their numbers. The two species certainly share nesting sites, but so far as I can gather (having done a very small amount of research on the web) there is no hard evidence to suggest that yellow-legged gulls regularly kill Audouin’s chicks. If the available supply of food was insufficient to meet their needs then I suppose they might attack the Audouin’s, but as it is there is a plentiful supply of “easier game” at the local dump.

I would imagine that the decline in numbers of Audouin’s might be related to a decline in fish stocks – because these guys are not scavengers; they only eat fish. That having been said, numbers of Audouin’s are said to be increasing now. There are two new colonies in the vicinity of the Mar Menor.

we have reared a chick for the last 6 weeks and it has always been attacked by other seagulls and finally this week he learned to fly only to be attacked by about a dozen or more adults while in the air we havent seen him back in garden for the last 6 hours im afraid the others have killed him.